SUMMARY: The goal of this R43 SBIR grant application is to understand the role of genetic variation in LMNA. For clinicians, the functional significance of 39.6% of the variations in LMNA have the status of being either unknown or a Variants of Uncertain Significance (VUS). As genomic sequencing continues its expanded utilization into the clinic, diagnostic rates will improves as variant function becomes better assigned to either pathogenic or benign status. Animal models have consistently been used as a proxy to understanding variant function. This proposal uses expression of a LMNA cDNA as a gene substitution of the orthologous gene of C. elegans animal model. With 79% of human genes having an identifiable homology in C. elegans, the extension of this humanization process to thousands of genes is possible. This proposal has three specific aims. The first aim is find a recoded version of the human LMNA cDNA that can be insert as a replacement of the orthologous C. elegans lmn1 gene and exhibit a capacity to rescue the function absent in the null allele. In the second aim, known pathogenic and benign variants are installed in the humanized locus and activity defects of the installed variants are measured. In the third aim, variants of uncertain significance and unknown status are installed in the humanized locus and measured for deviance of activity. In future Phase II work, once variant functional behavior is measured, drug activity can be explored for capacity to reverse phenotypes back to wildtype behavior.